In the construction of commercial offices and buildings, stairway construction frequently involves the fabrication of stringer weldments comprising metal channel beams to which are welded a plurality of carrier angle elements which function to locate and support tread and riser elements. In the past, a great deal of time and expense has been involved in the fabrication of these weldments because of the relative non-standardization thereof. Thus, while a given multi-level stairwell may utilize a plurality of stringer weldments of similar configuration, there is nevertheless a wide variety of configurations, resulting from the fact that differences in floor-to-floor dimensions and/or differences in stair angles imposed by designer election and/or physical requirements of the structure, require both the angular orientation and the nose-to-nose spacing of the carrier angles to be varied from structure to structure.
Pursuant to the present invention, a highly simplified and inexpensive fixture is provided, which can be set up expeditiously with relatively unskilled labor and which serves to provide precise positioning, orientation and spacing of carrier angle elements in a succession of stringer weldment assemblies. Because of the simple and expeditious set-up capability, the fixture may be used to great advantage, even in the production of a one-off pair of stair stringer weldments. More significantly, in a typical relatively short run, of a plurality of weldment assemblies for a given commercial structure, extremely asignificant production savings may be realized at an extremely modest investment in the fixture equipment and set-up time.
In accordance with the invention, the new fixture assembly includes spaced clamping means, which are securable to the edge flanges of the stringer beam elements. A straight edge reference beam is secured by the clamping means to the beam, and provides a longitudinally extending reference edge against which a series of carrier angle nesting blocks is positioned.
Each of the new fixture assemblies includes a plurality of carrier angle nesting blocks, each provided with a reference dowel positioned against the straight edge of the reference beam. A removable angle gage is temporarily mounted in each nesting block, as it is positioned against the reference beam, and precisely establishes the angular orientation of the nesting block relative to the longitudinal axis of the stringer beam. A quick acting clamp then secures the nesting block in position.
After properly locating and claimping the first of a series of nesting blocks, subsequent nesting blocks are mounted and secured, one at a time, using a spacing gage which is precisely adjustable in advance according to the desired nose-to-nose spacing of the carrier angle elements. To advantage, the spacing gage mounts on the same reference dowels that are used to position the nesting blocks against the reference beam.
Desirably, the fixture assembly of the invention, when fully set-up, includes a small plurality (e.g. five) of nesting blocks secured to the reference beam. After placement and welding of as many carrier angle elements as are accommodated by the number of nesting blocks, the entire fixture is shifted longitudinally along the stringer beam so that a relatively short fixture can accommodate the fabrication of stringers of any length. Further, the fixture is two-sided in that it can be transferred from a "left-hand" stringer to a "right-hand" stringer for the fabrication of matching, opposed stringer pairs.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.